Use "map of string" for query_parameters

Hi! The current syntax for query_parameters uses a "map of list of string". I know it's the same in AzAPI but I'm wondering if there really is a reason to use this complex format, or if you could reconsider this for msgraph and use a simple map instead? I pretty much always forget the brackets :(

It's also confusing because headers uses "map of string".

# Current syntax
query_parameters = {
  "$select" = ["id,mailNickName"]
}

# Proposed syntax
query_parameters = {
  "$select" = "id,mailNickName"
}

No files or tests are named. Search the provider for the query_parameters and headers schema, then inspect how query parameters are serialized and covered by tests. Done means the simpler map-of-string syntax is supported consistently without regressing existing Microsoft Graph requests.